Although several members of the class of organic thiocarbonates have been known for many years and various routes have been employed for their synthesis, the s,s′-bis-(α,α′—disubstituted—α″—acetic acid)—trithiocarbonate compounds of the present invention have not been disclosed. Trithiocarbonate compounds have been claimed for various applications, such as pesticides for agriculture, and also as lubricating oil additives.
Traditional methods of producing block copolymers, such as by living polymerization or the linking of end functional polymers, suffer many disadvantages, such as the restricted type monomers which can be utilized, low conversion rates, strict requirements on reaction conditions, and monomer purity. Difficulties associated with end linking methods include conducting reactions between polymers, and problems of producing a desired pure end functional polymer. The s,s′-bis-(α,α′—disubstituted—α″—acetic acid)—trithiocarbonate compounds of the present invention can alleviate the above noted problems and difficulties when utilized in free radical polymerizations.
The prior art WO98/01478 reference discloses the use of thiocarbonates to conduct living free radical polymerizations. The reference is limited to alkyl and benzyl functional groups, and is unable to make any aryl or carboxylic acid substituted trithiocarbonates with general methods known to the art. Synthesis, p 894 (1986), J. Chemical Research (Synopsis), p478 (1995), and Synthetic Communications, Vol. 18, p 1531 (1988). We have also found the conversion for the dibenzyl derivatives disclosed in their example 26 to be very slow compared to the present invention when polymerizing acrylate, as can be seen in the Example section of this application.
The ability of a brittle or thermoset epoxy resin to absorb energy without catastrophic failure can be increased through flexibilizing or toughening. Such flexibilizing and toughening may be accomplished by reacting or compounding the epoxy resin with an elastomer thereby enhancing the resin system's ability to resist mechanical and thermal stress. Such elastomers are known and include reactive liquid polymers such as carboxyl-terminated polymers as exemplified by U.S. Pat. No. 3,285,949, and amine-terminated polymers as disclosed in U.S. Pat. No. 3,823,107. It is also known that liquid carboxyl-terminated polymers have the advantage of a material which is pourable and castable at room temperature and because of the reactive functional chain ends it can be further reacted at elevated temperatures by the addition of polyamines or diepoxies to form the liquid diamine or diepoxy terminated polymers. Such liquid elastomers have found a wide variety of utility, but are particularly useful as toughening agents in sealants, caulk, adhesive and potting epoxy resin systems.
U.S. Pat. No. 3,285,945 relates to the production of liquid, carboxyl-terminated polymers, and more particularly relates to the use of a certain class of catalysts in combination with a particular solvent for the production of difunctional carboxyl-terminated butadiene polymers.
U.S. Pat. No. 3,770,698 relates to phenol terminated elastomers prepared by reacting carboxyl terminated polymers of dienes with diphenols such as bisphenol A, so that the carboxyl groups become part of the molecular chain and phenolic hydroxyls become end groups.